95 pontiac trans am with 10 speakers

I have a 98 Z28 that had the factory monsoon system and most of the speakers are 2ohm. Due to this, aftermarket speakers

would not be advised. They will sound better, but volume will be decreased.

Umm... Some punctuation and capitalization would have been nice.  It would make it far easier to read.  Would the trans am happen to be the one on your sounddomain page?

Anyhow, scrap all that junk.  Replacing the factory speakers with aftermarket ones will not yield a result that would be worth the cost (assuming around $100 per pair, times 3 = 300), IMO.  I think your looking for more clarity/volume and a little better sound quality?  Since your talking about just replacing the speakers I am assuming you are not trying to win any SQ contests so...  Working with the number 300, do this:

Replace the front speakers with a set of coaxial speakers http://www.cardomain.com/item/PIOTSA1670R?vq_id=none  purchase a 10 or 12 subwoofer  http://www.cardomain.com/item/MTXT6104A  New deck http://www.cardomain.com/item/PIODEHP3600?vq_id=none This pioneer deck can have the rear channels bridged to 70rms to drive the sub, it also has the crossovers you need to start.  Now your at 235 + shipping, lets call it 265.  Throw in 25 or 30 for a subwoofer box, and your still under budget.  This would almost surely be louder or as loud with more clarity then your factory deck on aftermarket speakers.

You can really do things with this setup in the future!  For around $100-140 add a (cheap) 4 channel amp http://www.cardomain.com/item/JBLP804Z , 2 channels for the front and 1 bridged for the subwoofer.  That would make a huge improvement in your sound quality and volume (I would recommend just breaking for it from the start, once you get some real power to those speakers you'll be shocked).  For another 120 http://www.cardomain.com/item/PIOTSC1653?vq_id=none add a set of components up front and move the 6.5 coaxials to the rear, your suddenly louder, clearer and have better imaging.  Want it even louder?  Add a subwoofer ampf or around 120-150, http://www.cardomain.com/item/PHOT2502 and use the 4 channel to power your components and rear coaxials.

You can do this a dozen ways.  Start with the deck, coaxials and a combo sub setup like this http://www.cardomain.com/item/MTXRTP212R, then you only need a 4 channel amp and components.  Or start with the components (no coaxials) 4 channel amp, subwoofer, and deck, and you have a great setup from day one.  The deck, components, coaxials would be a start under 300, if you added a 4 channel amp for those speakers you could have a punchy, clear system for under 350.  Later add a subwoofer and amp.  Plainly said:  STOCK SUCKS.

I have done the speaker swap in a 99 trans am (the interior is still the same) and it didnt sound all that bad. I mean its not going to be winning any trophies but I noticed a good sound improvement. The speakers I replaced were the front door components and the ones in the back seat. The speakers that were used were the polk DB series running roughly  (from a retail store not online, it might be cheaper online) 100 for the 6.5" and 150-170 for the components. I dont know if  you know this or not but the speakers in the back seat only put out lows, they are not a full range speaker stock. There is a factory amp located behind the pass. pannel right under the speaker that has the crossover built into it so if you do replace the speakers dont expect to get highs out of them unless you rewire the system. I left the wiring the way it was and the polks sounded better than the factory "mini woofers". As for the speakers in the hatch area the customer didnt want those replaced but the overall sound was great just leaving those stock. I'm not sure what size they are in the back for the monsoon system but I myself own a 95 formula without the monsoon system but it still has the 10 speaker system. The speakers in the back look like a 6x9 but if you take the pannel off it is actually a 4" speaker with a 1" tweeter. I would assume it would be the same for the monsoon.

Hope this helps

Thats ok, ; ). But I'll defend what I have written by saying... 

1.  That deck has the ability to bridge the two rear channels to 70 rms.  I will be the first to tell you deck power is nothing like a separate amp, I have demonstrated this to people using a pioneer amp I had in my daily driver civic, it was 25x4.  Sounded nothing like any deck that advertised 25x4.  Anyhow, I have a pioneer deck that does this, they call it "subwoofer drive" and I use it in my 83 chevy reg cab with a 6.5 inch bazooka tube (rated 100w rms for the sub).  The deck does not extract all of the potential from the bazooka, but it does a fair job.

2. I'll quote myself, "I would recommend just breaking for it from the start, once you get some real power to those speakers you'll be shocked."  "It" being the JBL 40x4 amp.  That amp could be ran 40x2 to the components and 160x1 to the subwoofer, JBL is a respectable brand and the power output can be believed.   If you do not think that is better then the "monsoon" system that comes stock, you need to give a similar system a listen.

3. "The speakers in the car are amplified, and dropping new equipment in may require removing the amps or rewiring."  Yeah, and if they are considering replacing every speaker in the car.. that would not be a bitch of a task?  I am assuming that they have a basic knowledge of car audio, I would not consider this setup to be a hard one to install, just moderate.  If he was going to a shop, why would he be asking us for advice?  I guess I just assumed he would install it himself, if not all this is surely out the window, installation will probably be 35-50% of the budget.

4."but will not be worth the money/labor in this vehicle, especially by downgrading to 1 less set of speakers."  Yes, everyone knows that the way to get clear, full sound is by having more speakers.  Thats why car manufactures advertise '16 speaker bose' and '10 speaker monsoon' so you know how damn good it is!  16 speakers, woah.  Fact is, less is more.  Less of the junk, more quality speakers in the right locations given the right power = more sound.

This was in my last paragraph, "Or start with the components (no coaxials) 4 channel amp, subwoofer, and deck, and you have a great setup from day one."  The pioneer deck + the pioneer compnents + the MTX 6000 subwoofer + the jbl amp = good sound for 450$.  Yes, I am assuming he installs it himself.  So give a extra 50 for the installation and it beats the crap out of the the monsoon system.  Plus he is poised for further upgrades if he wants, its not a deadend.  I dont have much more to say on it, if you have not heard a simple setup like that, you need to go hear one.  Peace.